books.google.it - A comprehensive, worldwide treatment of all groups of bees - 1200 genera and subgenera, including more than 16,000 species. In extensive introductory sections, Charles D. Michener examines the evolution of bees from wasps, the relations of the families of bees to one another, the evolution of bees in...https://books.google.it/books/about/The_Bees_of_the_World.html?hl=it&id=bu_1gmY13FIC&utm_source=gb-gplus-shareThe Bees of the World